Always breathe musically! Recently I had the pleasure of sitting next to Jim Markey with the Boston Symphony. I'm sure most people are familiar with the trajectory of Jim's career. Tenor trombone with the Pittsburgh Symphony, New York Phil, New York Phil on Bass trombone! and finally Bass trombone with the Boston Symphony.
We were playing a concert of film music by John Williams and some of the pieces were written for four trombones and I was playing the 3rd trombone part (next to Jim.) Something struck me as I was sitting there - Jim Markey never takes an unmusical breath! Every breath he takes is musical in every piece we played!
He could have thought "oh this is just film music" or "it's another pops concert" but no. Every time he played he was making a musical phrase and taking musical breaths! It hit me so clearly that I need to think about this and do it as much as Jim does.
When was the last time you sat down with your excerpts and pieces and just analyzed them from the point of view of breathing musically? Maybe take a few practice sessions to take this approach and see how it influences your music making. I know that I am going to!